• Structural Engineering and Mechanics
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• 제42권4호
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• pp.449-469
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• 2012

For generally damped linear systems with repeated eigenvalues and defective eigenvectors, this study provides a decomposition method based on residue matrix, which is suitable for engineering applications. Based on this method, a hybrid approach is presented, incorporating the merits of the modal superposition method and the residue matrix decomposition method, which does not need to consider the defective characteristics of the eigenvectors corresponding to repeated eigenvalues. The method derived in this study has clear physical concepts and is easily to be understood and mastered by engineering designers. Furthermore, this study analyzes the applicability of step-by-step methods, including the Newmark beta and Runge-Kutta methods for dynamic response calculation of defective systems. Finally, the implementation procedure of the proposed hybrid approach is illustrated by analyzing numerical examples, and the correctness and the effectiveness of the formula are judged by comparing the results obtained from the different methods.

• Earthquakes and Structures
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• 제5권3호
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• pp.359-378
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• 2013

The problem of identification of multi-component and (or) spatially varying earthquake support motions based on measured responses in instrumented structures is considered. The governing equations of motion are cast in the state space form and a time domain solution to the input identification problem is developed based on the Kalman and particle filtering methods. The method allows for noise in measured responses, imperfections in mathematical model for the structure, and possible nonlinear behavior of the structure. The unknown support motions are treated as hypothetical additional system states and a prior model for these motions are taken to be given in terms of white noise processes. For linear systems, the solution is developed within the Kalman filtering framework while, for nonlinear systems, the Monte Carlo simulation based particle filtering tools are employed. In the latter case, the question of controlling sampling variance based on the idea of Rao-Blackwellization is also explored. Illustrative examples include identification of multi-component and spatially varying support motions in linear/nonlinear structures.

• ETRI Journal
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• 제44권6호
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• pp.955-965
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• 2022

A low Earth orbit (LEO) satellite constellation could be used to provide network coverage for the entire globe. This study considers multi-beam frequency reuse in LEO satellite systems. In such a system, the channel is time-varying due to the fast movement of the satellite. This study proposes an efficient power and bandwidth allocation method that employs two linear machine learning algorithms and take channel conditions and traffic demand (TD) as input. With the aid of a simple linear system, the proposed scheme allows for the optimum allocation of resources under dynamic channel and TD conditions. Additionally, efficient projection schemes are added to the proposed method so that the provided capacity is best approximated to TD when TD exceeds the maximum allowable system capacity. The simulation results show that the proposed method outperforms existing methods.

• 한국철도학회논문집
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• 제17권5호
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• pp.321-327
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• 2014

본 연구에서는 구속된 다물체계의 비선형 운동방정식으로부터 QR분해법을 이용하여 선형 운동방정식을 유도하는 방법을 제시하였다. 다물체계의 선형 진동 방정식을 철도차량 대차에 적용하여 대차의 고유 진동모드를 구하고 레일의 변위 입력에 대한 대차프레임의 전달 함수를 구하여 대차의 진동 특성을 분석하였다. 대차의 고유 모드는 35Hz이하에서 나타났고 198Hz이상에서 국부모드가 계산되었다. 대차 프레임의 수직변위 전달함수는 수직변위 모드와 피치 모드가 속도에 영향을 받기 때문에 속도에 따라 변화하는 것으로 나타났다. 횡방향 전달함수는 매우 작게 나타났으며 전후방향 전달함수는 속도에 관계없이 전후방향 변위 모드가 주로 가진되는 것으로 나타났다.

• Journal of Information Processing Systems
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• 제12권1호
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• pp.46-56
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• 2016

Dynamic textures are videos that exhibit a stationary property with respect to time (i.e., they have patterns that repeat themselves over a large number of frames). These patterns can easily be tracked by a linear dynamic system. In this paper, a model that identifies the underlying linear dynamic system using wavelet coefficients, rather than a raw sequence, is proposed. Content based threshold filtering based on Set Partitioning in a Hierarchical Tree (SPIHT) helps to get another representation of the same frames that only have low frequency components. The main idea of this paper is to apply SPIHT based threshold filtering on different bands of wavelet transform so as to have more significant information in fewer parameters for singular value decomposition (SVD). In this case, more flexibility is given for the component selection, as SVD is independently applied to the different bands of frames of a dynamic texture. To minimize the time complexity, the proposed model is implemented on a graphics processing unit (GPU). Test results show that the proposed dynamic system, along with a discrete wavelet and SPIHT, achieve a highly compact model with better visual quality, than the available LDS, Fourier descriptor model, and higher-order SVD (HOSVD).

• 소음진동
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• 제9권4호
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• pp.849-855
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• 1999

신경망은 비선형 동적 시스템의 식별 및 제어에 대한 기존 방법의 매력적인 대체방법으로서 가능성을 보여주었다. 이 논문의 목적은 신경망의 응용, 즉 미지의 비선형 시스템의 입력 신호에 대한 신경 복원을 제시하고 있다. 이 기본 방법론은 여러 공학분야에서 실질적인 용도로 쓰일 수 있으며, 분명히, 이 제시된 기법의 응용은 시스템 입력을 측정하는 완전한 감지기망이 가능하지 않는 물리적 시스템에 중요할 수 있다. 또한 이 복원기법의 응용은 시스템이 정상적으로 작동할 시에는 중요하지 않지만, 성능저하 또는 시스템 중단을 야기하는 고장 혹은 시스템 이상을 일으킬 시에는 중요한 역할을 할 수 있다. 이 논문에서는 미지의 비선형 동적 시스템에 이 방법을 적용한 결과를 제시하고 있으며, 백색/채색 시스템 잡음에 대한 이 기법의 강인성이 평가되었다.

• East Asian mathematical journal
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• 제27권3호
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• pp.289-297
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• 2011

The introduction of fuzzy differential equation is to deal wit fuzzy dynamic systems. As classical differential equations, it is difficult to find the solutions to all fuzzy differential equations. In this paper an existence and uniqueness theorem for linear fuzzy differential equations is obtained. Moreover, the exact solution to linear fuzzy differential equation is given.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.1216-1221
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• 1990

An algorithm for multiple fault diagnosis of linear dynamic systems is proposed. The algorithm is constructed by using of the geometric approach based on observation that, when the number of faulty units of the system is known, the set of faulty units can be differentiated from other sets by checking linear varieties in the measurement data space. It is further shown that the system with t number of faults can be diagnosed within (t+1) sample-time units if the input-output measurements are rich and that the algorithm can be used for diagnosis even when the number of faults is not known in advance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.455-460
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• 2000

Impact occurs when the vibration amplitude of a mechanical component exceeds a given clearance size. Examples of these mechanical systems include impact dampers, gears, link mechanism, rotor rub, and so on. The vibration due to impact has strong non-linear characteristics, which cannot be predicted by usual linear analysis. The designs of mechanical systems with impacts should be done on the basis of overall dynamic characteristics of the systems. In this paper, the nonlinear behaviors of a beam with a periodically moving support and a rigid stop are investigated numerically and experimentally. The beam vibration with impact is modeled by the equations of motion containing piecewise linear restoring forces and by the coefficient of restitution, respectively. Experimental and numerical results show jump phenomena and higher-harmonic vibrations. The effects between the increase of stiffness during impact and the coefficient of restitution are investigated through the comparison of the experimental and numerical results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.558-561
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• 1993

The main difference between a linear system and a nonlinear system is the existence of direct interactions between input signals. These interactions will be classified into three types, (1) self-interaction among different order terms of control signals, (2) static mutual interactions between the control signals, and (3) dynamic interactions through the coefficient venctor fields of the control variables. In this paper, we will show that interactions of type (2) and (3) can be avoided by applying an appropriate dynamic compensator, while the interaction of type (1) is fatal.